On Saturday, water flooded the bus station, school, hotel and pedestrian zone in the centre of Golubac, the town where the Danube forms a natural border with Romania.
The rising level of four other rivers - Dunav, Sava, Tisa and Tamis - passing through Serbia led to the state of emergency in ten regions as citizens pitched in to help police and army units build defences against the floods.
Heavy rain and melting snow, have caused river levels to rise across the Balkans for a fifth straight day.
B92, a private radio station, reported that the most severe situation was in the town of Smederevo, some 40km east of the capital Belgrade, where hard machinery, sand-filled trucks and fire engines were deployed to build up new embankments.
Hundreds of houses were under water, and their inhabitants had to be evacuated.
The Danube's level reached 8.43 metre, some 40cm over its highest-ever level and it was expected to continue rising.
At least 300 houses were flooded and families forced to evacuate in Stari Kostolac, a municipality some 10km east of Smederevo.
In the Serbian capital, where the Danube meets the Sava river, some low-lying streets have been under water for several days, hampering traffic on at least one major road and forcing some evacuations.
Telephone communication was hindered in the parts of Belgrade located near the banks of the rivers, the telecommunication company said in a statement.
As water levels in both rivers passed record highs and were expected to peak overnight, the Belgrade authorities called on businesses and the local population to help shore up the city's defences with sandbagging and strengthening of dykes.
Srdan Jovanovic, chief of the capital's flood defence team, also made a special appeal to young women in Belgrade.
He asked that women who go out to Belgrade's famous float-clubs to stop walking over the sandbags and avoid making holes in them with their high-heeled shoes.